The compound [1R- (1.alpha., 2.beta., 3.alpha.) ]-2-amino-9- [2,3-bis (hydroxymethyl)cyclobutyl]-1,9-dihydro-6H-purin-6-one, i.e., ##STR1## is an antiviral agent with activity against herpes simplex virus type 1 and 2, varicella zoster virus, and human cytomegalovirus.
Norbeck et al. in European Patent Application 366,059 describe the preparation of this and related purinyl and pyrimidinyl antiviral agents by several routes. One disclosed process utilizes the conversion of the optically pure compound of the formula ##STR2## wherein R is an alkyl of 1 to 4 carbons as the starting material. This starting material is obtained by resolving the racemic Feist's acid with quinine according to literature procedures, e.g., W. von E. Doering et al., Tetrahedron, Vol. 26, p. 2825-2835 (1970).
Bisacchi et al. in U.S. patent application Ser. No. 451,664 filed Dec. 18, 1989, now U.S. Pat. No. 5,064,961 disclose preparing the antiviral agent [1R-(1.alpha., 2.beta.,3.alpha.)]-2- amino-9-[2,3-bis(hydroxymethyl)cyclobutyl]-1,9- dihydro-6H-purin-6-one from the intermediate ##STR3## wherein R.sup.4 is a protecting group such as benzoyl.